They found that children of parents with SMI had a 32 percent probability of developing SMI themselves by age 20, and this risk was more than twice that of control offspring. High-risk children had a significantly increased rate of developing the disorder present in the parent as well as of developing other types of SMI. For example, the risk of mood disorders was significantly increased among offspring of parents with schizophrenia, and the risk of schizophrenia was significantly increased in offspring of parents with bipolar disorder, but not among offspring of parents with depression.
The researchers said that their analysis "suggests that by early adulthood, the offspring has a 1-in-3 risk of developing a psychotic or major mood disorder a and 1-in-2 risk of developing any mental disorder."
For more information on the link between parental mental illness and such disorders in their offspring, see the Psychiatric News article, "Family Bipolar History Predicts Risk of Certain Childhood Disorders."